The Diamonds of Cempaka & Landak
During the height of the indian diamond trade in the 15th through 19th centuries, the diamonds from Landak, in Borneo (Kalimantan) were particularly prized for their brilliance and variety of colors. Borneo was part of the Dutch colonial empire (Dutch East Indies) from the 1600s to the early 1800s, when it came under the control of the 'British North Borneo Company.'
Borneo is now divided between Indonesia (the "Kalimantan" portion) to the south, Malaysia (the "East Malaysia" portion) and Brunei to the north, with a high mountain-range in the center of the island. West Kalimantan became an autonomous Province in 1957, with its capital being the port city of Pontianak.
Portuguese reports from the 1600s name Lawei and Tanjungpura as the regions that were the primary sources for diamonds, but these names are no longer used, and have vanished from any record. During this period, the mountainous central portion of the island was controlled by the aboriginal Dayak headhunters. During the 18th century, the Dutch produced approximately 50,000 carats of rough Borneo diamonds annually.
Photo (right): Kapuas River, Borneo (Author Unknown)
Borneo's 'Landak' diamonds were found by small-scale artisanal miners sifting through river-bank alluvial deposits in the southern and western part of the island. These rivers flow from the volcanic (diamondiferous) mountainous region at the center of the island. Landak's diamonds most likely came from the Landak river, and Kapuas river, both terminating near the coastal city of Pontianak. Secondary sources were from the river delta area around the coastal city of Banjarmasin.
Borneo's Geology
Borneo is the third largest island in the world, after New Guinea and Greenland. 'Landak' diamonds found on the island of Borneo, were created by the same geological forces that created the Himalayan Mountain range, and the "Ring of Fire" volcanic belt throughout Indonesia and the Pacific Rim. When the 'Tethys Oceanic Crust' collided and subducted under the 'Asian Continental plate' at rate of 10 centimetres per year, the fource caused volcanic activity which created diamondiferous intrusive and extrusive igneous rock known as 'kimberlite.'
Photo (right): NASA Satellite Photo of Borneo
Millions of years of erosion caused by rainfall, unearthed the diamonds from their kimberlite source, and washed them downstream to their final resting place in the alluvial river gravels of the Landak/Kapuas drainage basin and the Banjarmasin drainage basin to the southeast. No primary kimberlite or lamproite bodies have ever been located on Borneo, most likely due to significant erosion that took place millions of years ago. As such, all diamond production on the island is from alluvial secondary deposits.
West Kalimantan - Landak Diamonds
Diamonds in this region are found in the The 'Ngabang' area of West Kalimantan. The Gunung Niyut (Niyut Mountain 1701m) in western Kalimantan Barat province (below, left) was the likely source for the eroded diamond-bearing material that fed the Landak river. To the immediate south of Landak, the Kapuas River (the 'Mississippi of Borneo') is fed by the Gunung Lawit and Pegunungan Müller mountain ranges (2240m).
Borneo Map from 1800s
South Kalimantan - Cempaka Diamonds
South Kalimantan province is known as the 'Land of a Thousand Rivers.' Rainfall in the Pegunungan Meratus mountain range (1892m) in the south-eastern portion of the province (above, right) feeds into a massive drainage basin containing Riam Kanan Lake and the Barito, Murung, and Negara rivers that all empty into the sea at the Banjarmasin delta.
Small-scale artisanal mining continues to this day in South Kalimantan (Tengah Province), although Borneo is no longer considered a significant source for diamonds. The primary diamond-producing areas in this region are to the west of Riam Kanan Lake in the south, and the Upper Barito, Sungai Lahung, and Gula areas in Central Kalimantan. The Tengah Province capital of Martapura is known as the 'City of Diamonds.'
The villages of Lukaas and Sungai Tiung in Cempaka, southeast of Banjarmasin are a primary source for diamonds in South Kalimantan. Indigenous artisanal miners in this region still dig for diamonds, which are found in gravels and muddy sediments at depths of around 10 meters. The men dig in groups of 10 to 20 people, using baskets to bring up the slurry. When a pit is dug to the correct depth, horizontal tunnels are then dug to the sides.
Cempaka Miners - Photo: lovelos at pbase.com
The mud slurry is then poured into conical wooden bowls which are swirled around, so that the lighter material collecting towards the outside edge, while the heavier diamonds collect at the bottom.
South Kalimantan diamonds are classified as 'black' diamonds, 'colorless' diamonds, 'petrous' lower quality yellow diamonds, and 'pink' diamonds with high brilliance.
In 1965, a 166 carat pink diamond known as the "Trisakti Diamond," was found in the Cempaka region. The Indonesian Government had the rough stone cut by Joseph Isaac Asscher in Amsterdam, the same year.
